After a standard system upgrade you need to restart Firefox and any
applications that use xulrunner, such as Epiphany, to effect the necessary
changes.

Details follow:

Glenn Randers-Pehrson discovered that the embedded libpng in Firefox
did not properly initialize pointers. If a user were tricked into
viewing a malicious website with a crafted PNG file, a remote attacker
could cause a denial of service or possibly execute arbitrary code
with the privileges of the user invoking the program. (CVE-2009-0040)

Martijn Wargers, Jesse Ruderman, Josh Soref, Gary Kwong, and Timothee
Groleau discovered flaws in the browser engine. If a user were tricked
into viewing a malicious website, a remote attacker could cause a
denial of service or possibly execute arbitrary code with the
privileges of the user invoking the program. (CVE-2009-0771,
CVE-2009-0772, CVE-2009-0773, CVE-2009-0774)

A flaw was discovered in Firefox's garbage collection process. Under
certain circumstances a remote attacker could exploit this to cause a
denial of service or possibly execute arbitrary code with the
privileges of the user invoking the program. (CVE-2009-0775)

Georgi Guninski discovered a flaw when Firefox performed a
cross-domain redirect. An attacker could bypass the same-origin policy
in Firefox by utilizing nsIRDFService and steal private data from
users authenticated to the redirected website. (CVE-2009-0776)

Masahiro Yamada discovered that Firefox did not display control
characters in the location bar. An attacker could exploit this to
spoof the location bar, such as in a phishing attack. (CVE-2009-0777)